Set Harth is a Rogue Jedi. He only cares for worldly gain.. not any real ideology. He leaves the Jedi order to become a sort of darker Jedi version of Indiana Jones.
Anyway long story short, he is recruited by a sith to be her apprentice in the event that she beats her master (who she doesn't know has found a sith holocron describing the Sith power of Essence Transfer). Anyway he steals the holocron and runs away from the Sith with plans to live forever by having himself cloned and performing the essence transfer from clone to clone forever always avoiding being found by both Jedi and Sith.
IIRC this is basically what Sidious/Palpatine had been doing. So I figured he just took his time, all the while amassing a wealth of Sith knowledge and infiltrated the Sith pretending to be the apprentice to Darth Plageus until he learned how to create life from the force.
As an aside Lucas got the name "Sidious" from the word "insidious".
Definition of INSIDIOUS
1 awaiting a chance to entrap : treacherous b : harmful but enticing : seductive <insidious drugs>
2 having a gradual and cumulative effect : subtle <the insidious pressures of modern life> b of a disease : developing so gradually as to be well established before becoming apparent
Set was ambitious, just not in the same religious way Zannah and Bane were. His ambition was for power and wealth which seems to describe pretty much what Sidious was after too, doesn't it?
